any body running a vac pump? we used to in our speedway car and made good gains!

Rodney does. His came from $hawn Geer$
the yanks claim 20 hp.(probably 10 in Australia)
Even 10 would be worth the money spent.
...although you can spend couple of grand pretty quickly depending on whose you buy,
and what you spend on braided hoses and catch cans,
or how much stuff you want to make and experiment with.

I thinkl a gemini diesel had a pretty good pump on them, any other cars you know of?

early commadors

Vacuum pumps on diesels are for a different purpose. As many diesels don't pull any vacuum from the intake they require a vacuum pump to operate the brake booster. The vacuum pumps used on drag cars supposedly are meant to give a power boost by creating a vacuum in the crankcase and relieving blowby pressure.

While the proponents of vacuum pumps claim HP increases but I seriously doubt 10 to 20hp increase (if any) - Frankly I wouldn't waste my money. They were original put on drag cars that had large amounts of blowby out of ultra HP engines. The claims somewhat defy the laws of physics as to create the vaumm you need to put energy into driving the vacuum pump so how can you get more power out than you put in.

Ken

18 bhp on a fontana.also picked up a bit up a bit in mid range.
well worth the money if you are chasing an edge.
every engine is different so gains will always vary,but you can always play with pulley ratio's.
me personally,i have a million other things i can grap power from before i go down that road.i already have a full engine bay and don't need anymre headaches.

18 hp in how much? can you explain why there is a hp increase?

I think the reduction of

windage,
and
Pressure,
allows the components to rotate and reciprocate easier.

A dry sump pump with a large scavenge stage/stages,
can do the same.

It seems that vacuum creation does produce more power,
but the gains are actual,
not imaginary like with criogenics and coatings....

Ok physics can explain superchargers. Forcing air through a restricted intake system gets more air in the cylinder and the engine behaves as if it is a bigger displacement.

Vacuum in the crankcase makes it easier for the pistion to go down (in on a flat 4) but conversely makes it harder for the piston to go up ( out on a flat 4) so the net gain is zero. The only reason I can see is a greater pressure diffential accross the piston rings - so the rings seal better with less blowby - but 30 hp in 3000hp as a ratio is not worth worrying about on a 200hp engine and the loss with belt friction etc will probably offset any gains.

It does have the effect of lower oil pressure and that may give some gains

The only reference to vacuum pump gains on the web is from those selling them - there is nothing in the technical literature from the SAE etc.

yeas a bloke I know fitted one to a Holden V8 years ago and there were gains in engine dyno power and times at the strip.Not sure how much - but it was the basis of an article in Street Machine; I think it was a Holden 2.8-litre 'Blue' six (VH series) exhaust pump

gains are made not from the vacuum itself butyou can run lower tension rings and that there is less oil in suspention floating around for the crank to run into. ang a lovely by product is that you get almost zero oil leaks!!!!

The only thing that can explain a slight power increase (20hp in 3000hp!) is the advantage of lower tension rings and the greater pressure differential across the ring pack giving better ring sealing and less blowby. You are right about the oil leaks too as the first use of them was to stop rocker cover and sump gaskets blowing out on nitro cars!

On most of the VW engines we drive I can see no advantage and a lot more hassle cluttering up the engine bay, with another drive belt.

yes but we arnt talking about a 1600 dp!!!!!!!

20 hp in 3000Hp is 0.6% so even on a 300hp super hot VW engine this is only 2hp and I guarantee the losses in the belt drive of the vacuum pump will probably exceed 2 hp - so the net gain is Zero - so forget it!

The gains are outright.
Net, not grosse.

The gains, wether 10, 20 or 30hp, are seen on engines from small to big, and not just 1000hp prostock V8s.
The fontana above that Westi mentioned was probably a 250 to 300hp inline 4 cylinder that is used for speedway.
The figure I was told for a V8 speedway engine was 20hp on a 700 hp 370 ci engine.

If the gains on a volksy were 10hp,
net
I think it may be worth chasing if you have exhausted all other avenues.

In my case I think I would go for a big dry sump pump to get some gains and improve the oil system at the same time.

Most engine builders and dyno operators in the racing world claim just going to a basic drysump system
reduces windage enough to show a net gain in power and torque despite the extra power needed to run them.

I guess we'll have to agree to disagree - just can't see anyway a 5% gain in power can be had by having a vacuum pump attached to the sump. If it helps you go faster then good luck - I'll be proven wrong.

Ken